A multi-core cable has a structure in which a plurality of electrical wires are covered by a sheath that is made of an insulating resin material, and, conventionally, a seal structure (water stop structure) for the terminal portion of a multi-core cable is disclosed in JP 2012-182924A (referred to as Patent Document 1 hereinafter). In this seal structure, terminal processing is performed on the multi-core cable to branch off each electrical wire from the terminal of the sheath, a hot-melt block that includes partition walls for partitioning the electrical wires from each other is attached to the branched-off electrical wires, and then a heat-shrink tube is placed over the group of electrical wires so as to surround the terminal of the sheath. Thereafter, heat processing is performed to melt the hot-melt block and fill the gaps between the electrical wires so as to waterproof the spaces between the electrical wires, and then the heat-shrink tube is heated so as to shrink, thus preventing the intrusion of water from the group of electrical wires into the terminal of the sheath.